Synchronization Protocol For Networks Research Articles

A Mixed Approach for Clock Synchronization in Distributed Data Acquisition Systems.

Proper timing synchronization is important when data from sensors are acquired by different devices. This paper proposes a simple but effective solution for System on Chip (SoC) architectures that integrates a general-purpose Field Programmable Gate Array (FPGA) with a CPU. The proposed approach relies on a network synchronization protocol implemented in software, such as Network Time Protocol (NTP) or Precision Time Protocol (PTP), and uses the FPGA to generate a clock reference that is maintained in step with the synchronized system clock. The clock generated by the FPGA is obtained from the FPGA oscillator via appropriate fractional clock division. Clock drift is avoided via a software program that periodically compares the FPGA and the system counters, respectively, and adjusts the fractional clock divider in order to slightly adjust the FPGA clock frequency using a Proportional Integral controller. A specific implementation is presented on the RedPitaya platform, generating a 1 MHz clock in step with the NTP synchronized system clock. The presented system has been used in a distributed data acquisition system for fast transient recording in the neutral beam test facility for the ITER nuclear fusion experiment.

Proposed method: mean delays synchronization protocol (MDSP) for wireless sensor networks

PurposeMany synchronization approaches are based on low-level time capturing, causing a tight integration with the Media Access Control (MAC) layer. Alternatively, this study aims to present a hybrid approach combining both receiver–receiver and sender–receiver schemes to reduce the variation of two-way message exchange durations, in heavy-load networks. To achieve network-wide synchronization, a variant of Prim’s algorithm (Cormen et al., 2009) is used to build a spanning tree, guaranteeing the minimum number of ancestors and limited error propagation. The simulation results show that the proposed approach is very competitive with a set of the most-cited synchronization protocols. In addition, a new synchronization simulator SynSim was developed using C++ languageDesign/methodology/approachTo achieve network-wide synchronization, a variant of Prim's algorithm (Cormen et al., 2009) is used to build a spanning tree, guaranteeing the minimum number of ancestors and limited error propagation.FindingsSimulation results show that the proposed approach is very competitive with a set of the most-cited synchronization protocols. In addition, a new synchronization simulator SynSim was developed using in C++ language.Research limitations/implicationsIt can be concluded from the experiments that MDSP is suitable for WSNs especially if MAC layer timestamping is not possible. So, the mean delays synchronization protocol (MSDP) is suitable to achieve time synchronization in single-hop and multi-hop networks without the MAC layer timestamping in large wireless sensor network (WSN) deployments.Practical implicationsA future enhancement of MDSP could be switching between the traditional timestamping and the new proposed timestamping based on a given threshold, which is the number of nodes in the neighborhood and the load of the network. It will be also interesting to test it in a prototype. The proposed solution can be used in practice to implement the Time-division multiple access (TDMA) protocol in a WSN. In addition, the proposed simulator can be used in a computer network synchronization protocols course.Originality/valueTo the best of authors’ knowledge, this study’s contribution is original. In addition, the authors implemented a new synchronization simulator

IEEE 1588 High Accuracy Default Profile: Applications and Challenges

Highly accurate synchronization has become a major requirement because of the rise of distributed applications, regulatory requests and position, navigation and timing backup needs. This fact has led to the development of new technologies which fulfill the new requirements in terms of accuracy and dependability. Nevertheless, some of these novel proposals have lacked determinism, robustness, interoperability, deployability, scalability or management tools preventing them to be extensively used in real industrial scenarios. Different segments require accurate timing information over a large number of nodes. Due to the high availability and low price of global satellite-based time references, many critical distributed facilities depend on them. However, the vulnerability to jamming or spoofing represents a well-known threat and back-up systems need to be deployed to mitigate it. The recently approved draft standard IEEE 1588-2019 includes the High Accuracy Default Precision Time Protocol Profile which is intensively based on the White Rabbit protocol. White Rabbit is an extension of current IEEE 1588-2008 network synchronization protocol for sub-nanosecond synchronization. This approach has been validated and intensively used during the last years. This paper revises the pre-standard protocol to expose the challenges that the High Accuracy profile will find after its release and covers existing applications, promising deployments and the technological roadmap, providing hints and an overview of features to be studied. The authors review different issues that have prevented the industrial adoption of White Rabbit in the past and introduce the latest developments that will facilitate the next IEEE 1588 High Accuracy extensive adoption.

Clock Synchronization in Wireless Sensor Network With Selective Convergence Rate for Event Driven Measurement Applications

In this paper, a novel wireless sensor network synchronization protocol for event-driven measurement applications is proposed. The objective is twofold: 1) to provide high accuracy in the area where an event is detected and 2) to ensure a long network lifetime. The complexity of the problem arises from the fact that these two properties are usually in conflict. To increase the synchronization accuracy, nodes are required to exchange synchronization packets at higher rate, thus impacting the network lifetime. Vice versa to ensure a long network life time, the number of packets to be exchanged should be minimized thus impacting the synchronization accuracy. A tradeoff can be achieved by observing that the packet rate should be increased only for the portion of the network surrounding the detected events as only these nodes require a higher accuracy to collect data. The proposed algorithm represents a formalization of this idea. Numerical and experimental results are provided to validate the effectiveness of the proposed algorithm. 0018-9456 © 2014 IEEE.

GPS and IEEE 1588 synchronization for the measurement of synchrophasors in electric power systems

In modern transmission and distribution networks, monitoring, control and protection tasks are usually performed by Intelligent Electronic Devices (IEDs), that are often connected to each other by suitable communication links. Many of the procedures implemented require that the acquired data have an extremely accurate common time reference, with typical synchronization specifications ranging from milliseconds to a few hundreds of nanoseconds, according to the different use foreseen for the measured data. The strictest synchronization requirements lead to the need of highly accurate clock settings, such as the ones bases on satellite systems (e.g. the Global Positioning System, GPS). As an alternative, in situations where many devices are located in a geographically limited sub-area of the system, it could be advantageous to distribute the time reference to the remote stations through suitable network synchronization protocols. Between them, the PTP (Precision Time Protocol) defined in the Standard IEEE 1588 offers the best accuracy. This possibility is investigated in this paper, with special reference to one of the most challenging measurement problems, that is represented by the measurement of synchrophasors. Experimental results will be provided to evaluate the performance achievable with this solution.

A Kalman Filter Approach To Clock Synchronization Of Cascaded Network Elements

The Precision Time Protocol specified by IEEE 1588 standard has been proved to be an appropriate network synchronization protocol. The PTP protocol is based on exchanging appropriate timing information, generated by time stamping according to the local clocks, between adjacent clocks. Using the time-stamps, a slave element learns the relation between its own clock and the master clock so that it can synchronize its time to the reference time provided by the master. Uncertainties, e.g., random stamping and quantization errors, greatly affect the synchronization precision. This paper presents a probabilistic state-space model which quantifies the uncertainties and represents the relation between the system variables. Then clock synchronization is posed as a state estimation problem and solved by using Kalman filter. The performance of this approach is verified by numerical results.

Enhancement of the Precision Time Protocol in Automation Networks with a Line Topology

The precision time protocol (PTP) delivered by the IEEE 1588 standard has been proven to be an appropriate network synchronization protocol, which is widely applied in the areas of industrial automation, measurement and control, telecommunications and more. Many factors restrict the performance of the PTP protocol. In this paper, we highlight the influence of frequency drift on the synchronization performance. Based on analytic study, we develop an algorithm to improve the protocol, which is verified by simulation.

A PI Consensus Controller for Networked Clocks Synchronization

In this paper we propose a novel distributed clock synchronization protocol for networks of clocks which have different initial offsets and internal clock speeds. The algorithm is based on an PI-like consensus protocol where the proportional (P) part compensates the different clock speeds while the integral part (I) eliminates the different clock offsets. This synchronization protocol is formally studied in its synchronous implementation and we provide both convergence guarantees as well optimal design using standard optimization tools when the underlaying communication graph is known. We also show how this protocol can be readily used to study the effect of noise and external disturbances on the steady-state performance. Finally, some simulations are presented.

A scalable synchronization protocol for large scale sensor networks and its applications

Synchronization is considered a particularly difficult task in wireless sensor networks due to its decentralized structure. Interestingly, synchrony has often been observed in networks of biological agents (e.g., synchronously flashing fireflies, or spiking of neurons). In this paper, we propose a bio-inspired network synchronization protocol for large scale sensor networks that emulates the simple strategies adopted by the biological agents. The strategy synchronizes pulsing devices that are led to emit their pulses periodically and simultaneously. The convergence to synchrony of our strategy follows from the theory of Mirollo and Strogatz, 1990, while the scalability is evident from the many examples existing in the natural world. When the nodes are within a single broadcast range, our key observation is that the dependence of the synchronization time on the number of nodes N is subject to a phase transition: for values of N beyond a specific threshold, the synchronization is nearly immediate; while for smaller N, the synchronization time decreases smoothly with respect to N. Interestingly, a tradeoff is observed between the total energy consumption and the time necessary to reach synchrony. We obtain an optimum operating point at the local minimum of the energy consumption curve that is associated to the phase transition phenomenon mentioned before. The proposed synchronization protocol is directly applied to the cooperative reach-back communications problem. The main advantages of the proposed method are its scalability and low complexity.

Multimedia synchronization protocols for broadband integrated services

Protocols to provide synchronization of data elements with arbitrary temporal relationships of both stream and non-stream broadband traffic types are proposed. It is specified that the provision of a synchronization function be performed within a packet switched network, and, accordingly, a two-level communication architecture is presented. The lower level, called the network synchronization protocol (NSP), provides the ability to establish and maintain individual connections with specified synchronization characteristics. The upper level, the application synchronization protocol (ASP), supports an integrated synchronization service for multimedia applications. The ASP identifies the temporal relationships among an application's data objects and manages the synchronization of arriving data for playout. The proposed NSP and ASP are mapped to the session and application layers of the open-systems-interconnection (OSI) reference model, respectively. >